It is well known to measure the pressure of a liquid by using a pressure sensor. During a measuring process, generally the pressure sensor will be in contact with the liquid to be measured. In particular, the liquid passes into the pressure sensor and contacts a sensing element, so that the pressure of the liquid can be measured.
In some case, the liquid passed into the pressure sensor may be frozen due to such as a low temperature and converted into solid phase, which will cause a volume expansion and thus the damage of the components of the pressure sensor, particularly the components which are in contact with the liquid, for example the sensing element.
It is well known that a mass of contamination emission may be generated in industrial applications. For example, a mass of exhaust containing nitric oxides (NOx) will be discharged from the vehicle. Many technical solutions have been developed to reduce these emissions. Selective catalytic reduction (SCR) is one solution that is widely used.
In most selective catalytic reduction system, aqueous urea solution (AUS) is generally used as a working medium, such as 32.5% aqueous urea solution, so as to reduce the content of the nitric oxides. In recent selective catalytic reduction system, a urea pressure sensor (UPS) is generally used to monitor the pressure of the aqueous urea solution, to ensure normal operation of the selective catalytic reduction system. During operation, a portion of the urea pressure sensor (e.g., the sensing element) will be in contact with the aqueous urea solution, so as to measure the pressure of the aqueous urea solution.
However, with respect to the selective catalytic reduction system, a key technical problem is that the aqueous urea solution will be frozen at a temperature of about −11° C. or less. The volume of the aqueous urea solution will be increased after being frozen, so that a contact force between the aqueous urea solution and the sensing element of the urea pressure sensor will be increased, which will result in damage of the components (e.g., sensing element) of the urea pressure sensor in contact with the aqueous urea solution.
In the case of using a selective catalytic reduction system, such as in a vehicle, it is possible for the system to be subjected to a temperature of about −11° C. or less. In this case, it is a challenge how to address the effect of the frozen aqueous urea solution to the operation of the selective catalytic reduction system.